Method of making container caps



y 30, 1940, J- M. MONTELIONE .209.416

' IETHODUF HMKING CONTAINER CAPS Filed Oct. 26, 1934 s Sheets-Sheet 1 ATTORNEY y 30, 1940- J. M. MONTEL IONE 2.209.416

7 METHOD OF MAKING CONTAINER CAPS Filed Oct. 26, 1934 3 Sheets-Sheet 2 INVENT OR JEJEPH M Mo/vrEuo/vE ATTORNEY July 30, 1940- JL M. MONTELIONE 2.209.416

-- METHOD OF MAKING CONTAINER CAPS Filed Oct. 26, l934 3 Sheets-Sheet 3 I INVENTOR 103 JOSEPH M MONTEL/0NE in BY I06 1 w [09 o ATTORNEY V Patented July 30, 1940 UNITED STATES PATENT OFFICE METHOD or MAKING CONTAINER CAPS York . Application October 26,1934, Serial No. 750,036

10 Claims.

My invention relates particularly to improved methods for making single-piece sheet-metal caps or closures used for sealing the openings in containers, jars, cans or bottles, in which the cap 5 seals the container orifice when affixed in sealing position and locked by screw threads outside the contour of the nozzle or neck of the container.

These screw-threads are preferably formed on the inturned inner shell integral with'the cap skirt, and are adapted to engage suitable threads or lugs on the neck of the container.

Present commercial requirements for such screw-thread cap closures formed of a single piece of sheet metal are, (1) that the outer depending skirt shall be uniformly cylindrical and also present a smooth exterior surface throughout its entire area to allow for lacquering of the sheet metal without showing any indentations resulting from the embossing of the inner screw threads; (2) that the lower edge of the skirt be formed with a rounded head that lies in the same horizontal plane throughout its circumference in mutual parallelism with the top or crown of the cap; and 3) that the rounded screw threads be the cap skirt without any raw edges of the sheet material comprising this inner shell carrying the screw threads projecting anywhere inside the cap, and also without injuring the lacquer coating applied to the sheet metal before it isformed into the completed cap.

A closure cap of this type is described and claimed in my pending application for patent filed in the Patent Oflice October 12, 1934, Serial No. 748,030. g.

l The principal object of my invention is to provide a simple, effective and economical method of embossing or forming the screw threads on the inner cylindrical shell integral with the cap skirt when shaping the cap closure, so as to obtain an improved single-piece cap that will embody the several commercial requirements I have mentioned.

Further objects of my invention and advantages derived from following my improved methods for shaping and making these single-piece caps will be hereinafter described.

In the accompanying drawings,

Fig. 1 is a sectional elevation of the essential parts of a stamping machine for bending and shaping the sheet-metal from which my improved cap-closure is constructed;

Fig. 2 is an enlarged side elevation, partly in section, of a detail of this machine with the upformed on an inner cylindrical shell integral with turned cap in its initial form showing its crown or top and the up-turned flanged skirt;

Fig. 3 is an enlarged section of the cap showing the initial rolling over or bending of the lower margin of the cap skirt shown in Fig. 1 as a result of the operation of the parts shown in Fig. 2;

Fig. 4 is an enlarged partly sectional view, similar to Fig. 2, showing the cap rolled as in Fig. 3 with a different die and ready for the second rolling or curling operation on the cap skirt;

Fig. 5 is a view similar to Fig. 4, but showing the parts at the end of the second operation with the lower margin of the cap skirt rolled to form the inner cylindrical shell in which the screwthreads are embossed, an enlarged section of the cap being illustrated in Fig. 8;

Figs. 6' and 7 are two detail views showing enlarged sections of the cap in successive stages of development as the cap skirt is rolled from its Figs. 3 and 4 position to that shown in Figs. 5 and 8;

Fig. 8 is an enlarged section of-the cap shown in Fig. 5 as a result of the second operation in rolling inwardly the cap skirt;

Fig. 9 is a sectional elevation of a stamping machine showing a plurality of expanding leaves for impressing the screw threads outwardly and radially in the inner cylindrical shell shown in Fig. 8;

Fig. 10 is an enlarged top plan view showing the cap and expanding leaves as a result of the third operation by which major portions of the screw-threads are impressed in spaced-apart relation on the cylindrical inner shell of the cap;

Fig. 11 is a view similar to Fig. 10, but showing the tool containing the expanding leaves shifted approximately 45 to complete the formation of the continuous screw-threads on the inner shell 1 of the cap;

Fig. 12 is a side view, partly in section, of the completed cap;

Fig. 13 is a side view, partlyin section, of the essential parts of a thread-rolling machine showing a modified formof my improved methods for embossing the screw threads starting with the form of cap shown in detail in, Fig. 3;

Fig. 14 is a side view, partly in section, of the parts shown in Fig; 13, but brought together in operative relation with the cap in position to have the screwthreads impressed on the inner cylindrical shell;

Fig. 15 is a side view, similar to Fig. 14, showing thread-rolling tool bearing against the inner. shell of the cap to form the screw threads; and

Fig. 16 is a detail plan view showing the operation of the thread-rolling tool in embossing the screw-threads on the cap shell as shown in Fig. 15.

Similar numerals and letters refer to similar parts throughout the several figures.

Referring to Figs. 1-8 of the drawings showing the first and second curling or rolling action on the lower margin of the cap skirt, the cap or closure is initially stamped from sheet-metal by any well-known machine to comprise the top or crown l1 and depending cylindrical skirt l8 as shown in Fig. 2. Such sheet metal may advantageously be coated with lacquer or other similar materials for decorative purposes on the outside of the cap as well as the inner shell before such cap closure is initially stamped to form the cup-shaped closure shown in Fig. 2.

This Fig. 2 cap is then brought in position in the stamping machine shown in Fig. 1 with the raw edge IQ of the cap skirt l8 extending circularly around the top rim of the cap with the crown I1 at the bottom preparatory for the first operation on the cap skirt.

The stamping machine shown in Fig. 1 comprises the bed-plate 28 having the cylindrical hollowed-out portion 2| to enclose the annular anvil 22 fastened by screws 23 to the anvil holder 24 having the boss 25 that fits into the bed-plate 20. Within the bore of the anvil 22 is the anvil pad 26 that rests on the anvil holder 24 with the anvil pad spring 21 bearing on the holder 24 and the crown 28 of the anvil pad 26, which spring 21 forces the pad 26 upwardly until it engages the shoulder 29 on the anvil 24 to limit its upward movement.

Adjacent the sidewalls of the hollowed-out portion 2| is the pressure-pad bushing 36 within which is located the annular dial bushing pressure pad 3| that contains the dial bushing pressure pad springs 32. The dial bushing 33 encircles the anvil 22, and is adapted to fit in the annular space 34 formed in the dial 35 that is ziuiperimposed on the bed-plate 20 as shown in Referring to Figs. 1 and 2, the curling ring or die 36 is concentrically arranged over the anvil 22 within the annular space 34 of the dial 35, and such die 36 is fastened by set screws 31 'to the die holder 38 that is secured to the under side 'of the shank 39 by the binding screws 40. Surrounding the screw-threaded upper portion of the shank 39 is the adjusting nut 4| that is held in position by the set screw 42.

Slidably arranged within the die 36 is the cylindrical ejector 43 that is secured by locking pin 44 to the ejector stem 45 projecting upwardly through a hole in the center of the die holder 38 with the upper end of the stem 45 threaded to hold the ejector nut 46 and lock-nut 41 within the bore 48 of shank 39. Surrounding the ejector stem 45 is the ejector coil spring 49 that bears at its lower end on the ejector 43 and at its upper end on the die holder 38. The lower end of the ejector stem 45 contains the cylindrical bore 50 within which is the light coil spring 5| that normally forces downwardly the vacuum breaker pin 52 that slides in the bore 50 and through a hole in the center of the ejector 43 to release the cap from the ejector 43 when the latter is raised.

As shown in Fig. 2, the curling ring or die 36 contains a rounded notch 53 of small radius that encircles the die 36 with fiat side 54 that extends diagonally and radially toward the center of the die 36. After the cap is placed on the anvil 22 with the cap skirt l8 upwardly extended as shown in Fig. 2, the lowering of the shank 39 and associated parts shown in Fig. 1 when the machine is operated, brings the die 36 into contact with the raw edge I9 of the cap skirt l8. The continued descent of the die 36 causes the metal adjacent the raw edge I 9 to flow around the surface of the rounded notch 53 and follow the flat side 54 until such raw edge l9 strikes the side walls of the ejector 43 where its course is defiected downwardly to form the first roll or curling operation shown in enlargement in Fig. 3. Referring to Fig. 3 the section DE is formed and thereafter is not changed because as the raw edge I9 is thrust downwardly by the ejector 43, the entire section DE is pulled away from the flat side 54 of the die 36. As the die 36 continues its downward movement, the sheet metal continues to flow upwardly and around the notch 53, thereby forming the true are C (Fig. 3). As the section CF is forming, the raw edge I 9 is pushed over against the sidewall of the skirt I8 by the resistance of the radial section C--D already formed. When the section CF is formed the die 36 has reached the limit of its lowering movement (Fig. 1), and the cap takes the form shown in Fig. 3. When the die 36 is raised by the return orupward movement of the shank 39, the dial bushing 33 and dial 35 are then rotated a predetermined segment by the usual means in stamping machines of this type about the hub of the machine so as to transfer the cap shown in Fig. 1 to the second curling or rolling operation that will now be described.

This second operation as shown in Figs. 48 utilizes the same mechanism as in the first operation shown in Fig. l, and hence it need not be again described, except that a new curling ring or die 56 has been substituted for the die 36. This die 56 embodies the rounded notch 51 of a larger radius than the notch 53 as is shown in Fig. 4. When the cap shown in Figs. 1 and 3 -is placed on the anvil 22 (Fig. 4), the die 56 is in its raised position. When the die 50 starts its downwnard movement the preformed section CF engages the rounded notch 51, and as the sheet-metal flows around the notch 51, the raw edge l9 using the cap skirt l8 as a brace becomes a pivot center with the section C--D moving in a true arc, while the section F-J is being shaped as shown in Fig. 6. As the point D continues to move around the raw edge l9, the section F-J will be forced from a true radius to the straight section F-J shown in Fig. 7, because the raw edge 9 has been moved upwardly by the preformed sections D--E' and D-F, (Fig. '7). At the same time the section H-J (Fig. 7) has been shaped in a true are by the notch 51. As the die 56 continues its downward movement, the raw edge I9 is drawn away from the side walls of the skirt 18 by the rolled channel D-F until the straight section D-E is substantially parallel with the side walls of the cap skirt l8 as shown in Fig. 8, while at the same time the curved section HJ of Fig. 7 is further curled or rolled to the section J-K of Fig. 8, which shows the cap shell completely rolled and ready for the thread forming operations in the somewhat fiattened inner cylindrical shell 58 (Fig. 8) that extends between the two rolled portions or beads of the cap. The vacuum breaker pin 52 releases the cap from the ejector 43, when the latter is raised by the spring 5| pressing the tip of the pin 52 below the plane of the bottom of the ejector 43.

Referring to Figs. 8-12 of the drawings, I have here shown in Fig. 9 the essential parts of the machine used for impressing the screw-threads on the cylindrical inner shell 58 of the cap illustrated in Fig. 8. This press or stamping head comprises the bed-plate 59 that contains the anvil 68, the anvil pad 6|, and the anvil pad spring 62 similarly constructed to the corresponding parts in Fig. 1 that have been hereinbefore de-- scribed. The dial bushing pad 63 supports the dial bushing 64 within the bed-plate 59 upon the upper surface of which rests the dial 65. Fastened below the shank 68 by the guide screw 61 sliding in the slot 68 is the curling ring or die 69 between which die 69 and the shank 66 is the coilspring 10 enclosed in the bore 1|. The curling ring or die 69 has its cap-engaging portions 12 shaped similarly to the die 56 (Figs. 4 and 5) to hold the cap shaped as in FiQrS firmly in position on the anvil 68.

A plurality of expanding leaves 13 (four being shown in Figs. 10 and 11) are arranged within the die 69 at spaced intervals to allow for a rocking radial movement within the cap. The outer arcuate rims 14 of the leaves 13 carry the spiral convolutions to form the screw threads in the inner shell 58 of the cap when the leaves 13 are forced outwardly and radially against this inner shell 58. The shanks 15 of the leaves 13 have the beveled portions 16 above the rims 14 with. the projections 11 arranged on the inner sides of the shanks 15 above the beveled portions 16, while the outer tips 180! the shanks 15 form a fulcrum for the leaves 13 when the latter are rocked inwardly to clear the shell 58 of the cap.

Within the circular opening 19 of the shank 66 is the annular leaf holder 88 that is held in position by the key-pin 8| sliding in the slot 82 formed in the shank 66 (Fig. 9) while the coil spring 83 enclosed in the slot 84 in the shank 66 and the registering slot 85 in the leaf-holder 88 enables the latter to be held yieldingly in the shank 66.

concentrically disposed within the expanding leaves 13 is the leaf stem 86 having its lower end 81 cylindrically formed with the beveled flange 88 arranged adjacent to the beveled portions 18 of the expanding leaves 13, the upper rim of such flange 88 being adapted to coact with the leaf projections 11 to pull the leaves 13 inwardly to clear the cap shell 58. The upper portion of the leaf stem 86 is threaded to fasten same to the shank 66 as shown in Fig. 9.

Slidably supported in the leaf stem 86 is the ejector stem 89 with the ejector pad 98 pivoted on the pin 9|. The upper end 92 of the ejector stem 89 moves in the bore 93 formed in the shank 66 and the shank head 94, in which bore 93 is arranged the'ejector coil spring 95; the force of this spring 95 is regulated by the spring screw 96.

Fig. 9 shows this tool assembly in its closed po, sition with the leaves 13 pressed against'the cap shell 58. To release same, the shank 66 and the leaf-stem 86 begin'to lift as a unit and the straight portion 81 below the flange 88 clears the inner straight edges of the rims 1| of the leaves 13. At this time the top of the flange 88 engages the projections T1 and by the use of the tips 18 of the leaves 13 as a fulcrum, the rims 14 carrying the threaded parts of the leaves'13 'are pulled inwardly to clear the cap shell 58. 'During this upward movement of the shank 66 and leaf stem 86, all the other parts of this tool assembly have remained immovable, since they are held in position by the springs 18, 83, and 95, except the leaves 13 which have been moved inwardly and horizontally as just described.

As the leaves 13 complete their inward horizontal movement, the shank 66 strikes the head of the screw 61 to inaugurate the upward movement of the die 69, while the leaves 13 and leaf holder 88 are moved upwardly by the leaf 'stem 86. When the die 69 lifts, the dial bushing 64 follows the die 69 to be nested in the dial 65; as the die 69 clears the upper rim of the cap, the ejector pad 98 is raised by the upward movement of the leaf stem 86 acting on the upper end 92 .of the ejectorstem 89. When the pad 98 lifts, the anvil pad 6! is forced upwardly by the coil spring 62 to raise the cap to the level of the top surface of the bed plate 59, and the cap is ready to be the shank 66 and bring the tool assembly into closed portion with the leaves 13 expanded to impress the screw threads on the shell 58, the ejector pad 98 strikes the crown I1 of the cap and forces same into the nest of the anvil 68 while depressing the anvil'pad 6| which is resisted by the spring 62 and the spring 95 begins to compress. After the cap is so nested, the die 69 passes downwardly around the cap and strikes the dial bushing 64 which is forced downwardly with the' pad 63, which is closed when it reaches the bottom, and further downward movement of the dial bushing 64 and die 69 ceases. With these parts in fixed position, the coil springs 83 and 18 start to compress, and the bottoms of the leaves 13 engage the pad 98 which limits the downward movement of the leaves 13, at which time all the parts of this tool assembly except the shank 66 and leaf stem 86 have ceased further vertical movement.

As the leaf-stem 86 continues its downward movement, the cylindrical portion 81 strikes the beveled portion 16 of the leaves 13, thereby forcing them outwardly and horizontally so that their arcuaiie outer threaded rims 14 are embossed into the inner channel shell 58 of the cap (Fig. 8). Such embossing is completed when the lower end 81 of the leaf stem 86 reaches the limit of its downward stroke as shown in Fig. 9.

In this embossing of the screw threads in the shell 58 the leaves 13 impress their rims 14 except in the four spaced-apart segments shown at O in Fig. 10 where the shell 58 retains the ,gen-

eral contour shown in Fig. 8. In Fig. 12 the imprint of the leaves 13 is shown at R and S, section R showing the metal that flowed into the cavity between the threads on the leaf rims 14, while section S shows the metal stretched outwardly by such leaf threads. The rolled-over bead T is of slightly smaller radius in Fig. 12 than as shown in Fig. 8, which is due to the die 69 being pressed down firmly to prevent any metal creeping upwardly upon the expanding movement of the leaves 13, thereby forcing any excess move ment of sheet metal to flow downwardly within the interior of the cap to maintain its true height and contour while the section D-E of Fig. 8 is forced outwardly against the side wall of the cap skirt as shown atQ in Fig. 12.

The next operation is to impress the proper threads on the four segments 0 which were not embossed in the preceding step bya separate tool assembly.

The tool assembly of the second unit and its function are the same, but it is turned substantially 45 of the first unit that has hereinbefore been described. The leaves 13 of the second unit are identical in construction with the leaves 13 of the first unit, and they are similarly closed and inserted within the cap shown in Fig. 10, when the leaves I3 of such second unit are expanded to emboss the segments 0 as shown in Fig. 11 to complete the threads formed entirely around the inside of the cap shell 58 with the cap completely shaped for use as shown in Fig. 12, since the leaves I3 of both tool units are substantially the same except that the spaces between the leaves I3 of the second unit are arranged segmentally substantially 45 to those spaces in the first tool unit.

A modified method of forming the threads by rolling same on the cap shell 58 and starting with the cap as shown in Fig. 8, I have illustrated in Figs. 13, 14, 15 and 16. This mechanism comprises the thread roller holder 91 which revolves in a fixed position, and is the driving member to rotate the cap. The cap nest roller 98 rotates at a slower speed than the holder 91.

The roller 98 moves horizontally to the left (Fig. 13) until the cap is nested therein; the further movement of the roller 98 holding the cap in place is continued until the outer face of shell drive roller 99 contacts with the crown I 1 of the cap with this tool assembly revolving in closed position as shown in Fig. 14. At this moment the pressure roller I00 'is brought down vertically to strike the shell nest roller 98 to force the latter down until the thread roller I02 is embedded in the inner shell 58 (Fig. 15) Fig. 16 is a plan view of the thread roller I02 in threadembossing .position. At this moment the drive roller 99 has engaged the inner side wall surface of the cap skirt I8, and rotates the cap until the entire inner channel of the shell 58 is embossed with the threads formed on the peripheral face of the roller I02. When this embossment is completed (Fig. 12), the pressure roller I00 rises and the shell nest roller 98 is pushed back to its original position by the nest follower roller I03 which is constantly under the pressure of the spring I04 coiled about the pressure rod I05 slidably supported in the bracket I06 secured to the bracket IN. This bracket I01 is fastened to a horizontally reciprocating member (not shown) on which the shell nest roller 98 is slidably actuated by the rollers I00 and I03,-but is fixed horizontally to the horizontally reciprocating member (not shown) actuated horizontally by any conventional drum type of cam that is customarily used in these rolling machines. The rod I05 carries the pin I08 on which the follower roller I03 revolves, and the spring I04 is held between the collar I09 pinned to the rod I05 and the bracket IIO secured to the bracket I01. The pressure rod back stop I I I is pinnedto the lower end of the rod I05, all as shown in Fig. 13.

When the embossing of the threads is completed, the shell nest roller 98 moves horizontally to the right with the cap retained in the nest by the internal ejector II2 slidably supported in the drive roller 99 until the cap is entirely clear of such roller 99 when the internal ejector II2 snaps back to its original position at which time the external ejector II3 slidably supported in the nest roller 98 moves to the left to eject the cap which falls away, and then the tool assembly shown in Figs. 13-16 is ready to form by rolling the threads along the inner shell 58 of another cap.

In both forms of my improved methods for making the threads on the inner shell 58 of the cap. it will be observed that no female thread forming tool is utilized for embossing the threads on this shell 58, but the inherent stresses of the shell itself are employed to resist the force of the thread-forming members by which the required screw threads are embossed along the substantially flat section of the shell 58 adjacent and above the rounded bead T. In short I have dispensed with the use of coacting dies usually employed to emboss the sheet metal between them to shape the cap and form threads on the inner shell 58 thereof.

Various changes and modifications in the methods used in the apparatus hereinbefore described for practicing such improved methods may be made without departing from my invention and without sacrificing the advantages derived from their use.

I claim as my invention:

1. A method for making a single-piece sheetmetal can having a crown and a depending cylindrical skirt with a reentrant threaded -inner shell, which comprises rolling successive portions of the lower margin of the skirt interiorly of the cap and upwardly toward the crown to provide a uniformly rounded bead around the entire circumference of the skirt with the raw edge portion bent substantially semi-circular in crosssection within the bead adjacent the lower margin of the skirt to form a substantially flat inwardly presented circular surface in said cylindrical reentrant shell, said fiat surface being uniformly spaced from, and in mutual parallelism with, the lower margin of the skirt, and then embossing screw-threads in the said fiat inwardly presented surface of the said shell above the bead. while forcing only the bent-over raw edge portion of the shell against the inner sidewalls of the cap skirt.

2. A method for making a single-piece sheetmetal cap having a crown and a depending cylindrical skirt with a reentrant threaded inner shell. which comprises rolling successive portions of the lower margin of the skirt interiorly of the cap and upwardly toward the crown to provide a uniformly rounded bead around the entire circumference of the skirt with the raw edge portion bent substantially semi-circular in cross-section within the bead adjacent the lower margin of the skirt to form a substantially fiat inwardly presented circular surface in said cylindrical reentrant shell, said flat surface being uniformly spaced from, and in mutual parallelism with, the lower margin of the skirt, and then embossing screw-threads with a male threadforming tool bearing on the said fiat inwardly presented surface of the said shell above the bead, while forcing only the bent-over raw edge portion of the shell against the inner sidewalls of the cap skirt.

3. A method for making a single-piece sheetmetal cap having a crown and a depending cylindrical skirt with a reentrant threaded inner shell, which comprises rolling successive portions of the lower margin of the skirt interiorly of the cap and upwardly toward the crown to provide a uniformly rounded bead around the entire circumference of the skirt with the raw e'dge portion bent substantially semi-circular in crosssection within the bead adjacent the lower margin of the skirt to form a substantially flat upwardly presented circular surface in said cylindrical reentrant shell, said flat surface being uniformly spaced from, and in mutual parallelism with, the lower margin of the skirt and then embossing screw-threads with a male thread-forming tool moving radially and outwardly against said fiat inwardly presented surface of the said shell above the bead, while forcing only the bent over raw edge portion of the shell against the inner sidewalls of the cap skirt.

4. A method for making a single-piece sheetmetal cap having a crown and a depending cylindrical skirt with a reentrant threaded inner shell, which comprises first rolling the lower margin of the skirt interiorly of the cap to provide a substantially fiat exposed portion with its raw edge bearing against the cap skirt, then con-1 tinuing the further rolling of the skirt margin to bend the raw edge portion interiorly directed toward the bottom of the first roll so that such raw edge portion is substantially in mutual parallelism with the resultant skirt margin to form the cylindrical reentrant shell, and then embossing screw-threads in the inwardly presented surface of said shell, while forcing the outer margin of the shell against the inner sidewalls of the cap skirt. v

5. A method for making a single-piece sheetmetal cap having a crown and 9. depending cylindrical skirt with a reentrant threaded inner shell, which comprises first rolling the lower margin of the skirt interiorly of the cap to provide a substantially fiat exposed portion with its raw edge bearing against the cap skirt, then con tinuing the further rolling of the skirt margin to bend the raw edge portion interiorly directed toward the bottom of the first roll so that such raw edge portion is substantially in mutual parallelism with the resultant skirt margin to form the cylindrical reentrant shell, and then embossing spaced-apart sections of screw-threads by a thread-embossing tool in said shell, and finally presenting the partially threaded cap to a different thread-embossing toolof substantially the same spiral pitch to complete the continuous screw-threads on the inwardly presented surface of said shell, while forcing only the bent-over raw edge portion of the shell against the inner side-walls of the cap skirt.

6. A method for making a single-piece sheetmetal cap having a crown and a depending cylindrical skirt with a reentrant threaded inner shell,-which comprises first rolling the lower margin of the skirt interiorly of the cap to provide a substantially flat exposed portion with its raw edge bearing against the cap skirt, then continuing the further rolling of the skirt margin to bend the raw edge portion interiorly directed toward the bottom of the first roll so that such raw edge portion is substantially in mutual parallelism with the resultant skirt margin to form the cylindrical reentrant shell, and then partially forming with a series of outwardly expanding threaded tools arranged within the cap interrupted screw-threads on spaced-apart sections of the inner shell, and finally presenting the partially threaded cap to a difierent set of embossing tools of substantially the same spiral pitch and actuating said tools to complete the continuous screw-threads on the inwardly presented surface of said shell while forcing the outer margin of-the shell against the inner sidebent substantially semi-circular in cross-section within the'bead adjacent the lower margin of the skirt to form a substantially flat inwardly presented circular surface in said cylindrical reentrant shell, said flat surface being uniformly spaced from, and in mutual parallelism with, the lower margin of the skirt, and then embossing screw-threads by rolling with a single male,

thread-forming tool bearing on the said fiat inwardly presented surface of the said shell above the bead, while forcing only the bent-over raw edge portion of the shell against the inner side- 'walls of the cap skirt.

8. A method for making a single-piece sheetmetal cap having a crown and a depending cylindrical skirt with a reentrant threaded inner shell, which comprises rolling successive portions of the lower margin of the skirt interiorly of the cap and upwardly toward the crown to provide over raw edge portion of the shell against the imier sidewalls of the cap skirt.

9. The method claimed in claim 1 characterized by rolling successive portions of the lower margin of the skirt to cause the sheet metal to flow interiorly and involutely within the cap to form a reentrant cylindrical shell having a flat I0 inwardly presented surface substantially parallel with the cap skirt andconnected thereto by a uniformly radially curved portion forming the bottom rim of the cap.

10. The method claimed in claim 1 characterized by'rolling successive portions of the lower margin of the skirt to cause the sheet metal to flow interiorly and involutely within the cap to form a reentrant cylindrical shell having a flat inwardly presented surface substantially parallel Q with the cap skirt and connected thereto by a uniformly radially curved portion forming the bottom rim of the cap, the raw edge portion of the shell flowing outwardly adjacent the inner wall of the skirt.

JOSEPH M, MONI'EIIONE. 

